The effect of pressures up to 7 kbar on portions of
the Fermi surfaces of zinc and aluminum has been determined
by using the field-modulation technique to detect de Haasvan
Alphen oscillations and by using solid helium as a
pressure medium. The primary result obtained in the study
of zinc was that the (0001) cross section of the needle
portion of the Fermi surface doubled at 3 kbar. This
observed behavior is qualitatively in agreement with predictions
based on the near1y-free-e1ectron model. A
quantitative comparison with this model is complicated/by
critical dependence on the cia ratio.
The pressure dependence of two Fermi surface cross
sections of aluminum was observed. The V-(110] cross
section decreased 0.47 Z 0.06% per kbar while the S-[100]
cross section increased 1.2 ± 0.15% per kbar. The near1yfree-
electron model would predict an increase of 0.074% per
kbar for both of these cross sections. The departure of
the observed effects from this value is attributed to changes
in the band structure of aluminum, which the near1y-freeelectron
model does not take into account. A simple model
is described which utilizes the pressure dependence of the
pseudopotential coefficients to predict changes in the Fermi
surface cross sections with pressure. The effects predicted
by this model are of the correct order of magnitude and sign
to explain the experimental observations.